The invention relates generally to arc flash detection and, in particular, to arc flash sensors.
Electric power circuits and switchgear equipment have conductors separated by insulation. Air space often serves as part or all of this insulation in some applications. If the conductors are too close to each other or voltage exceeds the insulation level, an arc can occur between conductors. Air or any other insulation (gas, solid, or liquid) between conductors can become ionized, making the insulation conductive and thereby enabling an arcing event. Arc events may induce temperatures that can reach as high as 20,000° C., vaporize conductors and adjacent materials, and release an explosive energy that destroys surrounding circuits.
An arc flash is typically the result of a rapid energy release due to an arcing fault between two phases or between one phase and a neutral or ground. An arc flash can produce high heat, intense light, and acoustic waves similar to that of an explosion. However, an arc fault current typically includes a much lower magnitude as compared to a short circuit current, and circuit breakers do not necessarily react to such lower magnitudes of current. Typically, arc flash mitigation techniques use standard fuses and circuit breakers. However, such techniques have slow response times and are not fast enough to mitigate an arc flash.
One technique to mitigate arc faults is to reduce the response time of arc sensors. For example, reduced response time may be achieved by detecting specific characteristics of the arcing event such as light. Optical sensors detect light within an enclosure and determine the occurrence of the arc flash event. However, such a method of light detection may lead to erroneous arc detection when stray light or light from other sources is detected. Further, such methods do not provide information regarding the location of the arcing event. Other techniques include implementing pressure sensors within the enclosure to detect arc flash induced pressure changes. Such methods, however, result in delayed detection as pressure build-up takes a significant amount of time.
There is a need for improved arc flash prevention mechanism that has an improved response time and minimizes false alarms.